A nanotube gas ionization sensor built by researchers at the Rensselaer Polytechnic Institute could allow emergency crews to detect and identify gases swiftly in case of a terrorist attack. Traditional sensors take about five minutes to work and can be bulky (some measure 5 feet by 3 feet by 6 inches). The new device is not yet as sensitive as current sensors, but it is safer (uses lower voltage), provides instant results, and can fit in a half-inch cube.